#include <iostream>
#include <math.h>

using namespace std;

int main(int argc, char *argv[]) {
	long long n, sum=0, c=0;
	
	while (cin >> n) {
		sum += n;
		c++;
	}
	
//	cout << sum * pow(2, c-1) << endl;
	for (int i=1;i<=c-1;i++) {
		sum *= 2;
	}
	cout << sum << endl;
	return 0;
}